After a borehole has been formed into the ground, it is often desireable to test specific isolated geological stratas in order to determine the rate of production that can be realized therefrom. This is sometime carried out during the drilling of the borehole, and at other times the testing is carried out after the borehole has been cased, cemented, and while the drilling rig is still positioned over the borehole.
Barrington 4448254 discloses a flow tester valve apparatus which is responsive to annular pressure and which utilizes a liquid spring chamber.
Barrington 4444268 discloses a flow tester valve apparatus within which there is included a chamber filled with compressable liquid for actuating a power piston.
Helms 4125165 discloses a valve apparatus for use downhole in a bore hole and employes a piston which is responsive to trapped pressure in a pressure chamber and to annular pressure for controlling a valve.
Wray 3858649 discloses oil well testing and sampling apparatus which utilizes downhole pressure and a spring means to hold a valve means closed until the hydraulic pressure opens the tool to the formation and allows testing operations to be formed.
Holden 3856085 discloses a pressure responsive formation testing method and apparatus which utilizes the valve closing and the valve opening forces which are generated in response to annular pressure.
The present invention differs from the above cited art by the provision of a valve device which is actuated by elevating borehole upper annular pressure at a minimum rate to a predetermined magnitude. The present invention avoids the dangerous practice of using high dome pressure, and enables the valve actuator means to be located above a packer while the valve means is located below the packer. A mandrel is received through the packer and connects the actuator to the valve means. The valve means includes a novel sliding valve assembly as well as a novel ball valve assembly.
The sliding valve assembly has a port associated therewith which is brought into registry with a plurality of mandrel ports, and wherein the mandrel is moved uphole by a power piston and latched into alternate positions of operation by increasing the upper annular hydrostatic pressure. The movement of a latch means and the sliding valve are coordinated such that an increase in the annular pressure unlatches the mandrel and forces the mandrel to move uphole to the next latched position, with each successive latch position effecting an opened and then a closed valve configuration.